lakeffect2

Now that I have a wideband O2 sensor it I can start to see some problem areas in my programming. One of them is that it goes very lean after Hot Restarts. I'm on $8D running S_AUJP_V4

The AFR gauge will peg at 20, maxed out, and the engine will stumble and sometimes stall out. This is all while in open loop condition on a hot restart. Once it gets to closed loop it will run up to 14 or 13 on the AFR gauge. Along the way, I've likely altered some (maybe all?) of the parameters governing restart and temp related AFR stuff during open loop, including the O2 constants. So I would think there is a fuel vs temp related factor in open loop that I'm not catching on to?

Any suggestions as to where to start my hunt to enrich-en hot restart values?

Another issue is my AFR going very rich just barely fethering the throttle upward, It can go from 14's to 10's and 11's with barely any increase in rpm or change in vacuum (kpa) I was thinking that I have AE set to be too sensitive, that perhaps too slight of a % change initiates too large of a pump shot situation.

Make sense? Other factors?

lakeffect2

Any takers, ideas, thoughts on either question?. 38 views so far, no responses.

RBob

iTrader: (1)

This makes it difficult to tell you where to start. There is the open loop AFR vs MAP modifier table, the open loop AFR vs CTS modifier table, and the after start (choke) AFR tables. Compare them to a stock calibration and go from there.

There is also some hot restart logic in $8D. However, they are for SA and idle speed.

RBob.

lakeffect2

Thus far I've been working with the "Open loop Parameter, % change AFR vs coolant temp"

BY adding more to the table figures, the problem does not seem as severe or as often, but not totally cured yet.

RBob

iTrader: (1)

If still using a MAT sensor, it can help to change to an IAT. This is in both type of sensor and location.

RBob.

lakeffect2

RBob, in reference to your question, Yes I'm using a manifold air temp (MAT) sensor in it's original position in the back of the TPI plenum.

For practical purposes, I don't have a typical long underhood intake. It's a K&N tapered oval filter strapped to a 58mm throttle body. It might to possible to reposition the MAT sensor, or do you have thoughts on a IAT sensor in the filter area as an alternative? I can appreciate where that might sense colder air faster than a heat soaked MAT sensor.

Is that what you are suggesting? I'm on Speed density, 7730, $8d and using S_AUJP_V4 in Tunerpro RT (V4)

Dave

RBob

iTrader: (1)

The MAT sensors in the TPI plenums heat soak. Which is what causes the lean condition. Note that these sensors are all brass, just like a CTS.

Using a plastic MAT is helpful.

But better is using the bird cage style IAT sensor that measures the actual incoming temperature.

With the K&N on the TB, no place for an IAT. Try locating it so that it is right where the K&N is. Basically, right up against it (on the outside).

RBob.

lakeffect2

I went to Advance auto today to pick up a new sensor. It is all plastic and looks like it would plug into a grommet or rubber part. It was not threaded like the old brass one, and had a cage around what looked like a silver ball.

Pictures shown in a few MAT /IAT threads have shown plastic cages on metal threaded sensors, not all plastic. So I'm a little concerned that I have the right part, but figure all plastic is less prone to heat soak anyway.

I disconnected the original under-plenum sensor, lengthened the wires, and just happened to have a correct fitting plug kicking around that was used to get it attached. I mounted it in the rubber back edge of my K&N conical filter, so that it will be in the incoming airstream instead of being a heat soaked metal sensor stuck in the plenum.

Is there any distinction or change required in programming to accept new values or are both the IAT and MAT within reasonable working ranges of each other?

Darkness and brain cramp kept me from finishing. I'll be out first thing in the AM to finish up.)

doughboy2k3

I am having the same problem. Did installing the IAT sensor fix it.
Did you have to do any programming to accept the new values or did the ranges match up.
Also do you recall the part number for the IAT sensor you picked up. Thanks

lakeffect2

So far it seems to be working, but with limited opportunity to really test it under heat soaked conditions (haven't gone shopping much)

There was also a table I changed that was related to coolant temp while in open loop. It seemed to have a big deep dip in it from temp about 32-80C the same areas I was having issues with. So it seemed prudent to change that as well, raising the dip considerably as to add fuel during hot warm up, open loop conditions. That's where the issue was.

I'll report back in few days to let you know if the change was successful. I've been getting get a check engine light until it goes into closed loop. Only thing I see in the data log was the knock sensor, so I'll have to borrow a paperclip and jump the ALDL terminals to see what's there.

Dave

JP86SS

iTrader: (1)

This doesn't directly tie to the hot restart issue but has a good discussion on IAT/MAT changes needed.
https://www.thirdgen.org/forums/diy-...uys-ditch.html

lakeffect2

Now that the car has a few weeks of running under the swap, I can tell you this worked. The lean restart issue is gone. So I did two things specifically to correct it.

I swapped out and moved the MAT sensor. It is now the plastic birdcage style previously described. It plugs in, not screws in. The old sensor was left in place to seal the hole in the bottom on the plenum. The new sensor is in the rubber edge of my K&N filter, after lengthening the wires to reach.

Changes were made in the "open loop AFR vs CTS" table in the range from 32-80C. They were raised to have more fuel squirting in to correct the lean issue.


So far it works. Might need just a little more tweak in the open loop fuel table. The ECM light had previously lit up, staying on all the time while in open loop. Now, I'd say in 60 or so starts, I've seen it maybe three times, but went out quickly. Need to pull codes first. Before the changes, codes were for knock sensor, which considering all the lean kicking and bucking made sense to me.

My thanks to all who took the interest to respond.

Dave Buchholz

RBob

iTrader: (1)

The IAT you described a few posts up is for a TBI engine. They use a rubber grommet in the air cleaner to mount it.

RBob.

lakeffect2

Seeing as the K&N filter had a rubber mounting surround on it, the tbi version worked perfectly for this application. Thanks for the idea.